Silane compounds such as monosilane and disilane or chlorosilane compounds such as trichlorosilane, dichlorosilane, and tetrachlorosilane are used as a raw material for producing polycrystalline silicon required for the production of semiconductor devices or the production of solar cells (for example, Patent Literature 1: Japanese Patent Laid-Open No. 2012-153547).
Particularly, trichlorosilanes are important as a raw material for producing high-purity polycrystalline silicon, and examples of the known methods for producing trichlorosilanes include a direct method in which metallurgical-grade silicon and hydrogen chloride are reacted with each other (Patent Literature 2: Japanese Patent Laid-Open No. 2-208217, Patent Literature 3: Japanese Patent Laid-Open No. 9-169514) and a method in which tetrachlorosilane is reacted with hydrogen in the presence of metallurgical-grade silicon to reduce the tetrachlorosilane (Patent Literature 4: Japanese Patent Laid-Open No. 60-36318).
Incidentally, large amounts of boron compounds are contained in metallurgical-grade silicon. Therefore, if chlorosilanes are produced using metallurgical-grade silicon as a raw material, a boron impurity concentration in the resulting chlorosilanes will be about several ppm.
However, if polycrystalline silicon is produced using, as a raw material, chlorosilanes containing boron impurities at such a high concentration, the boron will be incorporated into polycrystalline silicon as an impurity and will act as an acceptor to significantly degrade the quality.
From such a background, various methods have been proposed as a method for removing boron impurities in a silane compound or a chlorosilane compound. Examples of the methods include an adsorption and removal method using a weakly basic ion-exchange resin (particularly, a weakly basic ion-exchange resin having a tertiary amine as an active group) (Patent Literature 5: International Publication No. WO 2011/24276, Patent Literature 6: U.S. Pat. No. 2,877,097, Patent Literature 7: U.S. Pat. No. 3,414,603).